Continuity mistake: Clark's dog leaves a baseball on the ground and walks until being parallel to Clark's both legs. A frame later the dog is two meters behind, next to Clark's left knee.
Continuity mistake: The writings on the note Lois faxes to the Daily Planet (with the coordinates) change from when she writes it to when Jimmy sees it through his camera. For example, the 'N' is much smaller and the 'P' is fatter in the faxed version. (01:31:45)
Continuity mistake: When Lois and Clark exit the building and she scolds him for leaving, the passers by don't match between one shot and the other.
Continuity mistake: After the plane has landed in the stadium and Superman is checking if the passengers are all okay, note the speaker's glasses. They alternate between being very crooked to being perfectly straight. (00:41:15)
Answer: There are two stories: a) the suit was made by Martha Kent from the blankets which came with Superman when he was a child and these blankets got superstrenght from the sun too. b) Superman generates an aura which protects him and his suit against such forces. Both stories can be true: either the suit itself is weakend by the kryptonite or Superman's aura was weakend by it. Currently it is said that the blanket-story is the correct one. Also, they don't actually cut it off him - it appears to open along a predefined line (coupled with someone exclaiming "got it!"), presumably the method Superman uses to get into the suit himself.
Bjoern_Buller